nzart-exam-generator/files/N28.TXT

% FILENAME = N28.TXT
% Propagation 
% Release version 3, October 2001

%QUESTION 1
#28.1 A 'skip zone' is:  

the distance between the antenna and where the refracted wave first 
returns to earth 

the distance between the far end of the ground wave and where the 
refracted wave first returns to earth 

the distance between any two refracted waves  

a zone caused by lost sky waves 

% ans 2 

%QUESTION 2
#28.2 The medium which reflects high frequency radio waves back to the earth's 
surface is called the: 

biosphere 

stratosphere 

ionosphere 

troposphere 

% ans 3 

%QUESTION 3
#28.3 The highest frequency that will be reflected back to the earth at any given time 
is known as the: 

UHF 

MUF 

OWF 

LUF 

% ans 2 

%QUESTION 4
#28.4 All communications frequencies throughout the spectrum are affected in 
varying degrees by the: 

atmospheric conditions 

ionosphere 

aurora borealis 

sun 

% ans 4 

%QUESTION 5
#28.5 Solar cycles have an average length of: 

1 year 

3 years 

6 years 

11 years 

% ans 4 

%QUESTION 6
#28.6 The 'skywave' is another name for the: 

ionospheric wave 

tropospheric wave 

ground wave 

inverted wave 

% ans 1 

%QUESTION 7
#28.7 The polarisation of an electromagnetic wave is defined by the direction of: 

the H field 

propagation 

the E field 

the receiving antenna 

% ans 3 

%QUESTION 8
#28.8 That portion of HF radiation which is directly affected by the surface of the 
earth is called: 

ionospheric wave 

local field wave 

ground wave 

inverted wave 

% ans 3 

%QUESTION 9
#28.9 Radio wave energy on frequencies below 4 MHz during daylight hours is 
almost completely absorbed by this ionospheric layer: 

C 

D 

E 

F 

% ans 2 

%QUESTION 10
#28.10 Because of high absorption levels at frequencies below 4 MHz during daylight 
hours, only high angle signals are normally reflected back by this layer: 

C 

D 

E 

F 

% ans 3 

%QUESTION 11
#28.11 Scattered patches of high ionisation developed seasonally at the height of one 
of the layers is called: 

sporadic-E 

patchy 

random reflectors 

trans-equatorial ionisation 

% ans 1 

%QUESTION 12
#28.12 For long distance propagation, the radiation angle of energy from the antenna 
should be: 

less than 30 degrees 

more than 30 degrees but less than forty-five 

more than 45 degrees but less than ninety 

90 degrees 

% ans 1 

%QUESTION 13
#28.13 The path radio waves normally follow from a transmitting antenna to a 
receiving antenna at VHF and higher frequencies is a: 

circular path going north or south from the transmitter 

great circle path 

straight line 

bent path via the ionosphere 

% ans 3 

%QUESTION 14
#28.14 A radio wave may follow two or more different paths during propagation and 
produce slowly-changing phase differences between signals at the receiver 
resulting in a phenomenon called: 

absorption 

baffling 

fading 

skip 

% ans 3 

%QUESTION 15
#28.15 The distance from the far end of the ground wave to the nearest point where the sky wave 
returns to the earth is called the: 

skip distance 

radiation distance 

skip angle 

skip zone 

% ans 4 

%QUESTION 16
#28.16 High Frequency long-distance propagation is most dependent on: 

ionospheric reflection 

tropospheric reflection 

ground reflection 

inverted reflection
 
% ans 1 

%QUESTION 17
#28.17 The layer of the ionosphere mainly responsible for long distance 
communication is: 

C 

D 

E 

F 

% ans 4 

%QUESTION 18
#28.18 The ionisation level of the ionosphere reaches its minimum: 

just after sunset 

just before sunrise 

at noon 

at midnight 

% ans 2 

%QUESTION 19
#28.19 One of the ionospheric layers splits into two parts during the day called: 

A & B 

D1 & D2 

E1 & E2 

F1 & F2 

% ans 4 

%QUESTION 20
#28.20 Signal fadeouts resulting from an 'ionospheric storm' or 'sudden ionospheric 
disturbance' are usually attributed to: 

heating of the ionised layers 

over-use of the signal path 

insufficient transmitted power 

solar flare activity 

% ans 4 

%QUESTION 21
#28.21 	The 80 metre band is useful for working: 

in the summer at midday during high sunspot activity 

long distance during daylight hours when absorption is not significant 

all points on the earth's surface 

up to several thousand kilometres in darkness but atmospheric and 
man-made noises tend to be high 

% ans 4 

%QUESTION 22
#28.22 The skip distance of radio signals is determined by the: 

type of transmitting antenna used 

power fed to the final amplifier of the transmitter 

only the angle of radiation from the antenna 

both the height of the ionosphere and the angle of radiation from the 
antenna 

% ans 4 

%QUESTION 23
#28.23 Three recognised layers of the ionosphere that affect radio propagation are: 

A, E, F 

B, D, E 

C, E, F 

D, E, F 

% ans 4 

%QUESTION 24
#28.24 Propagation on 80 metres during the summer daylight hours is limited to 
relatively short distances because of 

high absorption in the D layer 

the disappearance of the E layer 

poor refraction by the F layer 

pollution in the T layer 

% ans 1 

%QUESTION 25
#28.25 The distance from the transmitter to the nearest point where the sky wave 
returns to the earth is called the: 

angle of radiation 

maximum usable frequency 

skip distance 

skip zone 

% ans 3 

%QUESTION 26
#28.26 A variation in received signal strength caused by slowly changing differences 
in path lengths is called: 

absorption 

fading 

fluctuation 

path loss 

% ans 2 

%QUESTION 27
#28.27 VHF and UHF bands are frequently used for satellite communication because: 

waves at these frequencies travel to and from the satellite relatively 
unaffected by the ionosphere 

the Doppler frequency change caused by satellite motion is much less 
than at HF 

satellites move too fast for HF waves to follow 

the Doppler effect would cause HF waves to be shifted into the VHF 
and UHF bands. 

% ans 1 

%QUESTION 28
#28.28 The 'critical frequency' is defined as the: 

highest frequency to which your transmitter can be tuned 

lowest frequency which is reflected back to earth at vertical incidence 

minimum usable frequency 

highest frequency which will be reflected back to earth at vertical 
incidence 

% ans 4 

%QUESTION 29
#28.29 The speed of a radio wave: 

varies indirectly to the frequency 

is the same as the speed of light 

is infinite in space 

is always less than half the speed of light 

% ans 2 

%QUESTION 30
#28.30 The MUF for a given radio path is the: 

mean of the maximum and minimum usable frequencies 

maximum usable frequency 

minimum usable frequency 

mandatory usable frequency 

% ans 2 

%QUESTION 31
#28.31 The position of the E layer in the ionosphere is: 

above the F layer 

below the F layer 

below the D layer 

sporadic 

% ans 2 

%QUESTION 32
#28.32 A distant amplitude-modulated station is heard quite loudly but the modulation 
is at times severely distorted. A similar local station is not affected. The 
probable cause of this is: 

transmitter malfunction 

selective fading 

a sudden ionospheric disturbance 

front end overload 

% ans 2 

%QUESTION 33
#28.33 Skip distance is a term associated with signals through the ionosphere. Skip 
effects are due to: 

reflection and refraction from the ionosphere 

selective fading of local signals 

high gain antennas being used 

local cloud cover 

% ans 1 

%QUESTION 34
#28.34 The type of atmospheric layers which will best return signals to earth are: 

oxidised layers 

heavy cloud layers 

ionised layers 

sun spot layers 

% ans 3 

%QUESTION 35
#28.35 The ionosphere: 

is a magnetised belt around the earth 

consists of magnetised particles around the earth 

is formed from layers of ionised gases around the earth 

is a spherical belt of solar radiation around the earth 

% ans 3 

%QUESTION 36
#28.36 The skip distance of a sky wave will be greatest when the: 

ionosphere is most densely ionised 

signal given out is strongest 

angle of radiation is smallest 

polarisation is vertical 

% ans 3 

%QUESTION 37
#28.37 If the height of the reflecting layer of the ionosphere increases, the skip 
distance of a high frequency transmission: 

stays the same 

decreases 

varies regularly 

becomes greater 

% ans 4 

%QUESTION 38
#28.38 If the frequency of a transmitted signal is so high that we no longer receive a 
reflection from the ionosphere, the signal frequency is above the: 

speed of light 

sun spot frequency 

skip distance 

maximum usable frequency 

% ans 4 

%QUESTION 39
#28.39 A 'line of sight' transmission between two stations uses mainly the: 

ionosphere 

troposphere 

sky wave 

ground wave 

% ans 4 

%QUESTION 40
#28.40 The distance travelled by ground waves in air: 

is the same for all frequencies 

is less at higher frequencies 

is more at higher frequencies 

depends on the maximum usable frequency 

% ans 2 

%QUESTION 41
#28.41 The radio wave from the transmitter to the ionosphere and back to earth is 
correctly known as the: 

sky wave 

skip wave 

surface wave 

F layer 

% ans 1 

%QUESTION 42
#28.42 Reception of high frequency radio waves beyond 4000 km normally occurs by 
the: 

ground wave 

skip wave 

surface wave 

sky wave 

% ans 4 

%QUESTION 43
#28.43 A 28 MHz radio signal is more likely to be heard over great distances: 

if the transmitter power is reduced 

during daylight hours 

only during the night 

at full moon 

% ans 2 

%QUESTION 44
#28.44 The number of high frequency bands open to long distance communication at 
any time depends on: 

the highest frequency at which ionospheric reflection can occur 

the number of frequencies the receiver can tune 

the power being radiated by the transmitting station 

the height of the transmitting antenna 

% ans 1 

%QUESTION 45
#28.45 Regular changes in the ionosphere occur approximately every 11: 

days 

months 

years 

centuries 

% ans 3 

%QUESTION 46
#28.46 When a HF transmitted radio signal reaches a receiver, small changes in the 
ionosphere can cause: 

consistently stronger signals 

a change in the ground wave signal 

variations in signal strength 

consistently weaker signals 

% ans 3 

%QUESTION 47
#28.47 The usual effect of ionospheric storms is to: 

increase the maximum usable frequency 

cause a fade-out of sky-wave signals 

produce extreme weather changes 

prevent communications by ground wave 

% ans 2 

%QUESTION 48
#28.48 Changes in received signal strength when sky wave propagation is used are 
called: 

ground wave losses 

modulation losses 

fading 

sunspots 

% ans 3 

%QUESTION 49
#28.49 Although high frequency signals may be received from a distant station by a 
sky wave at a certain time, it may not be possible to hear them an hour later. 
This may be due to: 

changes in the ionosphere 

shading of the earth by clouds 

changes in atmospheric temperature 

absorption of the ground wave signal 

% ans 1 

%QUESTION 50
#28.50 VHF or UHF signals transmitted towards a tall building are often received at a 
more distant point in another direction because: 

these waves are easily bent by the ionosphere 

these waves are easily reflected by objects in their path 

you can never tell in which direction a wave is travelling 

tall buildings have elevators 

% ans 2